1. Field of the Invention
The present invention relates to synchro stabilizer circuits, and more specifically, to means for overcoming the effect of line voltage variations on synchro output signals.
2. Description of the Prior Art
The output voltages derived from synchro devices are a function not only of the variables being monitored, but also of the magnitude of the supply voltage. Thus in situations where the supply voltage cannot be precisely regulated, variations in the line voltage may seriously affect the accuracy of the entire synchro system. Present techniques for compensating for line voltage variations in synchro systems employ a separate gain programming circuit which scales the demodulated d.c. signal as a function of the magnitude of the supply voltage. However, in such systems, the phase difference between the input to the demodulator and the line voltage scaler produces d.c. signals which are essentially uncompensated at higher frequencies. The problem becomes particularly severe in aircraft applications, for instance, which normally utilize a 400 Hertz supply voltage and line voltage variations typically occur in the 1-70 Hertz frequency range. The present invention eliminates the need for separate gain scaling circuits and thereby provides considerable cost savings for systems using a single a.c. supply to demodulate several a.c. inputs. The present system also eliminates the need for precise matching of the phase shift of the demodulator and the scaler.